I"KM.\TION OF GERM LAYKRS IN ACTINIA r.EK.ML'HENSIS. 345 



ha .ined very nearly the appearance of the original 



lila-tul.i < clU. The endoderm cells have in\v become much 

 bro.ider in proportion to their height, tlu-ir cytoplasm is much 

 [ess d.-n-e than formerly, and take- the -tain- [ess readily, \vhile 

 the IHH l<-i have bi-come markedly le-- con-picuous. In -ome 

 ons, uherc the body of the embr\o i- mo-t contracted, espe- 

 cially about thi n of the forming -tomodeiim. the oiitline- 



o! the i-ndoderm cell- are \-r\ iudi-tinct , and indeed iinpo--ihle 

 lo m.iki- ..in al the proximal end- of the cell-. 



I eitl 7 .in.l ;. 



Iii d tO the int. :i.-n ,,t the optic. d na -ho\\ n 



in McMuiiiih'- I ig. [Q, I'l. XIII.. it i- int.-ir-t ii: . 

 m\ I ig. o. \\ith the ' of tin- mil': ' :// 



v;i\-n bj \ppellof. In the la-t iiu-nt i< nied form, \\heiv th<- eixlo- 

 <lenn arises \>\ di-lamination. thei LfS .it the time of the 



I'leaUiiu through o| the miUth o; ideil thinniiu 



I'nih i;ei-m la\er- at the point \\here the mouth >\ pciiiii'< \\ill 

 appear. When the mouth ha- leeii formed tlu- ti--ue- are \er\- 

 thin all around it, and in a longitudinal -ectioii there ap|iear- 

 , iln .lit the mouth thi- thin area in-tea<l of the more thickened 

 ana \\hich is found about the ^a-tro]iore <>i an iiua^in.: 

 trula. So that in some in-tance- at least, McMurrii h'- critici-m 

 of the interpretation of optie.il -ectin-. of \\hole mount- \\ould 

 not appl\ . 



